Defrosting mechanism



Nov. 24, 1931. 1.. H. VOLD 1 1,833,544

DEFROSTING MECHANISM Filed May 10, 1928 2 Sheets-Sheet 1 INVENTOR ATTORNEY Nov. 24, 1931. L. H. voLD 1,833,544

DEFROSTING MECHANISM Filed May 10. 1928 2 Sheets-Sheet 2 INVENTOR M L @&/

ATTORNEY Patent ed Noe 24. 1931 UNITED STATEISSIPATVENTI-JOFFICE, j

. 112L388. vow or nurmaxrmmsrrvma Y nmos'rme Application and my 10,

This invention relates to electrically operated refrigerators and more particularly to apparatus for securing automatic defrostation of the refrigerator freezer at predetermined timed intervals.

Inrefrigeration, a refrigerant, as for example sulphur-dioxidefls employed and the process of freezing consists of letting the liquid refrigerant boil in the freezer thereby 1o consuming heat which is taken from the freezing chamber. After the refrigerant has boiled'in the freezer, it is in a gaseous form and is compressed and transmitted to a condenser where it isagain liquefied and readyfor use. This is the general principle of operation of all refrigerating machines. The refrigerant boils at a certain temperature under a certain pressure and the greater the pressure the greater will be the heat required 80 for boiling.

In the present invention I utilize the variations in pressure as a means for regulating the operation of the compressor, and since as explained, the temperature requirements vary with the pressure to which the refrigerant is subjected, it is possible to control the temperature at which the refrigerant will boil, indirectly, by controlling the pressure.

In the accompanying drawings constituting a part hereof and in which like reference characters designate like parts, Fig.1 is a plan view of an operating mechanism embodying a snap switch and pressure responsive device which cooperate in accordance with the principles of my invention; Fig. 2 is a sectional elevational view thereof; Fig. 3 is a modification of the make and break contacts employed in-the switch shown inFig. 2; Fig. 4 is a section through the make and break contacts; Fig. 5 is an end elevational view of the pressure responsive device; and Fig. 6 is a similar view of a modification thereof.

. Referring to Fig. 2 of the drawings, the

structure therein illustrated comprises a bed plate 1 having end brackets 2 and 3 on which i are pivotally mounted a switch lever 4 and a spring box 5. 9

As shown in Figs. 5 and 6, an'elastic bellows 6 is supported on the bed plate 1 by is biased by a coil spring which is adjustable by a nut 22. The rod lever,

MECHANISM 1928, seri l no. 276,534.

rods 7 which support a block-8 that constitutes an abutment for one of the end plates 9 of the bellows anda block 10 is-held' in suitably spaced relation by studs 11 which, may constitute an" extension of the rod 7 or be separately bolted to the block 8. The end plate 9 of the bellows 6 is provided with a rod 12 'that is operatively disposed in a swivel block 13 having trunnions 14 which engagethe switch lever 4 and the rod'12 is further provided with flanged nuts 16 which constitute abutments for coil springs 17, which rest against the swivel block 13. The upper end. 7 or the bellows is provided with a conduit or suction line 18 leading to the low pressure side of the compressor which compresses the gaseous refrigerant after boiling in the freezing chamber. The bellows 6 expands and contracts in accordance with the pressure in the line 18 which is the pressure in the freezer; In the axial movement of the bellows rod 12 energy is stored up in the coil springs 17 in accordance with the resistance to movement of the switch lever 4 which is regulated by the spring box 5 in which a plunger 20 21, the tension of 20 is pivotally joined at 23 to the end of the switch lever 4. By adjusting the tension of spring 21 the switch lever 4 is operated in response to pressure in the bellows '6, but on accountof the coil spring 17 storing up the energy necessary for tripping the switch. variations in pressure are permissible in the bellows 6 within certain ranges without affecting the position of the switch lever 4.

In Fig 6 I have provided adjustable coil springs 25 on the rods 7, the springs resting against the plate 26 that is movable with the rod 12 and the tension of springs 25 is varied by the adjusting nuts 27 for a purpose to be hereinafter explained.

Again referring to Fig. 2 of the drawings, the switch lever 4 is provided with an insulating block 29 having a contact element SOsecured thereto which-cooperates with a pair of terminal blocks 31 mounted on a block 32 of insulating material that is fastened to the bed plate 1 by bolts 33. When the contacts are made a circuit is established between the terminal blocks 31- which are provided with terminals 34 to which an electrical conductor 35 is attached, this conductor including in its circuit an electrical motor for operating the compressor or pump of the refrigerating machine.

As shown in Fig. 3 of the drawings, a spring catch 36 may be provided on the switch lever 4 which functions to continue the contact with the terminal blocks 31 if the main contact block 30 and the terminal blocks 31 should be slightly separated before the switch snaps over.

. Mounted on the a frame 38 carrying a stud 39 on which is rothe switch members 30 and 31 will be posltion in it was brought by pressure in the bellows 6' tatably mounted a ratchet wheel 40. A spring arm 41 is mounted on the bed plate as shown and constitutes a fixer for the ratchet wheel 40. A prong 42 is fastened to lever 4 and is adapted to engage the teeth of the ratchet wheel and a catch 43 is pivotally connected at 44 to the switch lever 4 and is biased by a tension spring 45 against a stop 46 carried by the lever 4. As illustrated, the ratchet wheel is provided with teeth of uniform pitch and depth with the exception of the space 47 which is of a greater depth than the remaining teeth of the wheel explained. a

The operationof the device is briefly. as follows:

Assumin that the switch lever 4 is in the icated by the line F'G to which which corresponds to the pressure in the freezer to which it is connected by the suction line 18. In this position the motor drivin the compressor will be energized, since 1n this position of the switch lever, contact is made between the members 30 and 31 and the motor circuit established. The pressure in the freezer will fall and the bellows'will begin to contract storin up energy in the bottom spring which Wlll begin.

to exert a force against the swivel block 13. "This building of pressureagainst-the swivel block will constitute force e .shown in the parallelogram of forces which will overcome the resultant force of the sprin box 5 at which time the switch lever 4 wi snap over to.the position indicated by 'the line F-D. The prong 42 will engage a tooth of the ratchet wheel 40 in the upward movement of the lever 4 and as the contact of broken, the motor will be open circuited and de-energized. The freezer will then beat up and the pressure will rise and the switch mechanism will become responsive to the increased pressure through the bellows16 exerting pressure against rection.

The building up of pressure against the the switch lever 4 in the reverse di- .'be replaced'by other justable counterweight for example. The

base 1 is a support-ing for a purpose to be hereinafter by the switch lever 4 which is equivalent to the spring pressureagainst the lever, will overcomeithe resultant force of the spring box and again the lever will snap to its contact making POSi? tion, and in doing so, the catch 43 will engage-a tooth of the ratchet wheel 40 and index it around one tooth space; The spring box 5 with its spring 21 is illustrated as one form'of restraining means which may means such as an adsprmg box may produce variable pressure for different elongations of the spring 21 depending upon the length of the spring box and the number. of coils in the spring.

The counterweight would be theoretically' correct as it is constant.

' The spring arm 41 serves to closely center the ratchet and during the next stroke of the switch lever 4 the depression 47 of the ratchet wheel is brought into alinement with the prong 42 against which it must seat.

When the lever 4 ne'xtsnaps. to its contact breaking position, it will assume the position indicated by the line F-E at which position spring box 5 and lever 4 will assume a diiferent angle and, as seen from the diagram of forces, the force 9 or g, forces, will be insuflicient to overcome the resultant force of of spring box 5 being f or f, they are substantially equal since they are both established by the spring 21. Both the forces 9 and g are equivalents of spring ressure against the swivel 13 around the fu crum F under ordinary operating conditions, but in order to overcome the spring box with the lever in the position produced by the deep tooth 47 of the ratchet wheel, an additional pressure It must be added to g or in other words, the e uivalent pressure of g- .and It must be exerted the swivel 13 by the spring 17 before the lever 4 will snap back. Since such a force as'will store up sufiicient pressure in the sprin to snap the lever back-from its position can be produced only through the expansion of the bellows 6, a higher temperature must prevail in the freezer than that ordinarily available to produce the force necessary to' snap back the 'sw itch lever to its contact making position.

By varying the relative depths of the tooth the remaining teeth of the ratchet.

47 and wheel, the F-E position of the lever 4 can be established to be responsive to pressures corresponding to a given temperature in the freezer, as for example 34 degrees which would defrost the tubes or diaphragm as the case may be; e

With a switch and pressure responsive operating mechanism, as herein illustrated and described, defrostation of the freezer will take place at predetermined cycles, as for which are ordinary spring box 5. The force against example, once every 24 cycles or more, depending upon the number of teeth 1n the ratchet Wheel, and the defrostation is therefore automatic and positively accomplished.

Referring to Fig. 6, the ad'ustable springs 25 maybe employed to .pro uce an adjustment whereby a certain amount of pressure in the bellows is permitted without producing an effective force on the coil springs .17. For example, in the illustration the space between the plate 26 and block 8 may be taken up at atmospheric pressure by simply adjusting the nuts 27.

Although one embodiment of the invention has been herein illustrated and described, it will be obvious to those skilledin the art that various modifications may be made. in the details of construction without departing from the principles herein set forth.

I claim herein as my invention:

1. A switch mechanism for a refrigerating system comprising a switch lever, power means connected, to said switch lever re sponsive to fluid pressure, and energy storing means also connected to said lever, a ratchet wheel'the teeth of which constitute an abutment for the switch lever, said ratchet l my'hand. I

wheel being rotated by the movement of the switch lever whereby a new abutment is provi ded for said lever, for each operating cycle of the switch.

2. Apparatus as set forth in claim 1 in which the ratchet wheel is provided with teeth of different depths to constitute differently located abutments for the switch lever,

3. Apparatus as set forth in claim 1' in which the switch lever is provided with tension means adapted to hold it against the abutments of said ratchet wheel, and in which the teeth of the ratchet wheel are of different de ths whereby the switch lever is held in .di erent positions by its tension means.

In testimony whereof, I have hereunto set LARS H. VOLD. 

